Liquid crystal display device

ABSTRACT

A liquid crystal display device having brightness uniformity at its front and lateral sides is provided according to one or more embodiments. In one embodiment, the liquid crystal display device includes a reflection sheet reflecting light, an optical plate including a substrate for guiding light, a height-varying portion formed on one surface of the substrate, not facing the reflection sheet, and a prism pattern formed on the height-varying portion, and a plurality of light sources arranged on one lateral surface of the optical plate in a first direction so as to correspond to a position of the height-varying portion having a height not greater than an average height from the one surface of the substrate to the height-varying portion, wherein the prism pattern extends in a second direction substantially perpendicular to the first direction, and the average height is in a range of about 0.1% to about 10% of the thickness of the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority and benefit from Korean PatentApplication No. 10-2008-0098682 filed on Oct. 8, 2008 in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

1. Technical Field

Embodiments of the present invention generally relate to a liquidcrystal display device, and more particularly, to a liquid crystaldisplay device having uniform brightness distribution of its front andlateral sides.

2. Description of the Related Art

Liquid crystal display devices are one of the most commonly used flatpanel displays (FPD). Liquid crystal display devices, which may includetwo panels having a plurality of electrodes arranged thereon and aliquid crystal layer interposed between the two panels, control thetransmittance of incident light by applying voltages to the electrodesto rearrange liquid crystal molecules of the liquid crystal layer.

The liquid crystal display (LCD) device is not a self-emitting device.Hence, it may require a separate external light source for illuminatinglight. The external light source may be selected according to the size,use or purpose. Specifically, according to the type, the external lightsource may include, but not limited to, a point light source such as alight emitting diode (LED), a linear light source such as a cold cathodefluorescent lamp (CCFL), or a planar light source. As the external lightsource, a plurality of light sources may be arranged at a lateral sideof an optical plate of an LCD device, such as a mobile phone, a computermonitor, a TV, or the like.

A bright line may be formed in an emission side of a plurality of lightsources or a hot spot phenomenon may be generated at a liquid crystalpanel positioned in the vicinity of the light sources, so thatdeterioration of visibility can be induced to frontal and lateral sidesof the liquid crystal panel.

SUMMARY

Embodiments of the present invention provide a liquid crystal displaydevice having brightness uniformity at its front and lateral sides.

According to an embodiment of the present invention, there is provided aliquid crystal display device that includes a reflection sheetreflecting light, an optical plate including a substrate for guidinglight, a height-varying portion formed on one surface of the substrate,not facing the reflection sheet, and a prism pattern formed on theheight-varying portion, and a plurality of light sources arranged on onelateral surface of the optical plate in a first direction so as tocorrespond to a position of the height-varying portion having a heightnot greater than an average height from the one surface of the substrateto the height-varying portion, wherein the prism pattern extends in asecond direction substantially perpendicular to the first direction, andthe average height is in a range of about 0.1% to about 10% of thethickness of the substrate.

According to another embodiment of the present invention, there isprovided a liquid crystal display device including a reflection sheetreflecting light, an optical plate including a substrate for guidinglight, and a plurality of prism patterns extending in parallel to oneanother in a first direction on one surface of the substrate facing thereflection sheet, and a plurality of light sources arranged on onelateral surface of the optical plate in the first direction, whereineach of the of prism patterns has a height-varying portion and theplurality of light sources arranged so as to correspond to a position ofthe height-varying portion having a height not greater than an averageheight of the plurality of prism patterns.

According to still another embodiment of the present invention, there isprovided a liquid crystal display device including a reflection sheetreflecting light, an optical plate including a substrate for guidinglight, a first height-varying portion formed on one surface of thesubstrate, not facing the reflection sheet, and a plurality of firstprism patterns extending on the other surface of the substrate facingthe reflection sheet in parallel to one another in a first direction, aplurality of light sources arranged on one lateral surface of theoptical plate in the first direction, and a plurality of second prismpatterns extending on the first height-varying portion in a seconddirection substantially perpendicular to the first direction, whereineach of the plurality of first prism patterns has a secondheight-varying portion, and the plurality of light sources are arrangedso as to correspond to a position of the first height-varying portionhaving a height not greater than a first average height from the onesurface of the substrate to the height-varying portion and a position ofthe second height-varying portion having a height not greater than asecond average height of the first prism patterns.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the embodiments of thepresent invention will become more apparent by describing in detail oneor more embodiments with reference to the attached drawings in which:

FIG. 1 is a layout view showing a liquid crystal display deviceaccording to a first exemplary embodiment of the present invention;

FIG. 2 is a perspective view showing an optical plate for the liquidcrystal display device shown in FIG. 1;

FIG. 3 is a view showing a positional relationship between an opticalplate and a light source when viewed in the Y-axis direction shown inFIG. 2;

FIGS. 4A and 4B are photographic representations illustrating uniformityin the brightness distribution of the LCD device according to the firstexemplary embodiment of the present invention and an LCD deviceaccording to a Comparative Example;

FIG. 5 is a perspective view showing an optical plate for a liquidcrystal display device according to a second exemplary embodiment of thepresent invention;

FIG. 6 is a perspective view showing an optical plate for a liquidcrystal display device according to a third exemplary embodiment of thepresent invention;

FIG. 7 is a perspective view showing an optical plate for a liquidcrystal display device according to a fourth exemplary embodiment of thepresent invention;

FIG. 8 is a perspective view showing an optical plate for a liquidcrystal display device according to a fifth exemplary embodiment of thepresent invention;

FIG. 9 is a perspective view showing the bottom surface of the opticalplate shown in FIG. 8;

FIG. 10 is a view showing a positional relationship between an opticalplate and a light source when viewed in the Y-axis direction shown inFIG. 9;

FIGS. 11A and 11B are photographic representations illustratinguniformity in the brightness distribution of the LCD device according tothe fifth exemplary embodiment of the present invention and the LCDdevice according to a Comparative Example;

FIG. 12 is a perspective view showing an optical plate for a liquidcrystal display device according to a sixth exemplary embodiment of thepresent invention;

FIG. 13 is a perspective view showing the bottom surface of the opticalplate shown in FIG. 12;

FIG. 14 is a perspective view showing an optical plate for a liquidcrystal display device according to a seventh exemplary embodiment ofthe present invention;

FIG. 15 is a perspective view showing the bottom surface of the opticalplate shown in FIG. 14;

FIG. 16 is a perspective view showing an optical plate for a liquidcrystal display device according to an eighth exemplary embodiment ofthe present invention;

FIG. 17 is a perspective view showing the bottom surface of the opticalplate shown in FIG. 16;

FIG. 18 is a perspective view showing an optical plate for a liquidcrystal display device according to a ninth exemplary embodiment of thepresent invention; and

FIG. 19 is a perspective view showing the bottom surface of the opticalplate shown in FIG. 18.

DETAILED DESCRIPTION

Advantages and features of the embodiments of the present disclosure andmethods of accomplishing the same may be understood more readily byreference to the following detailed description and the accompanyingdrawings. The present disclosure may, however, be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe concept of the disclosure to those skilled in the art, and will onlybe defined by the appended claims. Like reference numerals refer to likeelements throughout the specification. Accordingly, in some specificembodiments, well known processing steps, devices or methods will not bedescribed in detail in order to avoid obscuring the disclosure.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

A liquid crystal display (LCD) device according to one or moreembodiments of the present invention may be used in a portablemultimedia player (PMP), a personal digital assistant (PDA), a portabledigital versatile disk (DVD) player, a cellular phone, and otherdevices. For explanatory convenience, the LCD device according to one ormore embodiments of the present invention will be described as beingused in a cellular phone. However, the embodiments of the presentinvention are not limited to this and include the above-mentioned LCDdevices.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a layout view showing a liquid crystal display deviceaccording to a first exemplary embodiment of the present invention.

Referring to FIG. 1, the liquid crystal display (LCD) device 100generally includes a liquid crystal panel assembly 130 and a back lightassembly 150.

Here, the liquid crystal panel assembly 130 includes a liquid crystalpanel 135 having a thin film transistor (TFT) substrate 133 and a colorfilter substrate 134, a liquid crystal (not shown), a driving IC 131,and a flexible printed circuit board (FPCB) 110.

The liquid crystal panel 135 is a device which displays imageinformation such as a character, a number, or an arbitrary icon byadjusting the transmissivity of light that passes through a liquidcrystal layer (not shown) according to the intensity of an appliedvoltage. The liquid crystal panel 135 includes the TFT substrate 133,the color filter substrate 134, and the liquid crystal (not shown).

The TFT substrate 133 includes a plurality of gate lines, a data line,and a pixel electrode. The gate lines extend in a transverse directionand transmit a gate signal. The data line extends in a longitudinaldirection and transmits a data signal. A pixel is connected to the gatelines and the data line and includes a switching element and a storagecapacitor.

Here, the switching element is formed at a cross-point of the gate lineand the data line, and the storage capacitor and a liquid crystalcapacitor are connected to an output terminal of the switching element.In addition, the switching element may be formed as a TFT usingamorphous silicon and poly-silicon as a channel layer.

The color filter substrate 134 is located on the TFT substrate 133 andincludes a color filter that represents red, green, or blue color in aregion corresponding to the pixel electrode so as to display color ineach pixel. Here, the color filter may be formed above or below thepixel electrode. In addition, a common electrode formed of a transparentconductive material such as indium tin oxide (ITO) or indium zinc oxide(IZO) is formed on the color filter.

The liquid crystal layer (not shown) is filled between the color filtersubstrate 134 and the TFT substrate 133 and has dielectric anisotropy.The thickness of the liquid crystal layer (not shown) may be, forexample, about 5 μm, and the liquid crystal layer may be twisted nematic(TN) arranged. The arrangement direction of the liquid crystal layer(not shown) may be changed by a voltage applied from the outside so thatthe transmissivity of light passing through the liquid crystal layer(not shown) may be adjusted.

The TFT substrate 133, the color filter substrate 134, and the liquidcrystal layer (not shown), which are elements for the liquid crystalpanel 135, constitute a liquid crystal capacitor. The liquid crystalcapacitor having the above structure according to one or moreembodiments may be connected to the output terminal of the switchingelement and the common voltage or a reference voltage.

The driving IC 131 is an integrated circuit (IC) which receives a gatecontrol signal, a data control signal, and a data signal related to thedata control signal from the FPCB 110 via an input terminal and providesa gate driving signal and a data driving signal to the gate line and thedata line formed on the TFT panel 133 via an output terminal. As such, adesired image can be formed on the liquid crystal panel 135.

The FPCB 110 is a kind of PCB which connects various electroniccomponents to a printed circuit original board or supports theelectronic components according to the circuit design of electric wires.The FPCB 110 may be flexible.

One end of the FPCB 110 is connected to an external PCB (not shown), andthe other end thereof is connected to an input terminal of the drivingIC 131. As such, the gate driving signal, the data driving signal, andthe data signal related to the data driving signal are transmitted tothe driving IC 131 from the external PCB.

The backlight assembly 150 according to an embodiment of the presentinvention includes optical sheets 141, a light source 142, an alignmentplate 143, a reflection sheet 146, an optical plate 200, an upperreceiving container 140 receiving them, and a lower receiving container160 combined with the upper receiving container 140.

The upper receiving container 140 has sidewalls formed along an edgeshaped of a rectangular opening, for example, and a predeterminedprotrusion (not shown) is formed in the rectangular opening formed bythe sidewalls, so that the upper receiving container 140 receives theoptical plate 141 and the liquid crystal panel assembly 130 and preventsthe sheets from sagging.

The FPCB 110 of the liquid crystal panel assembly 130 is bent centeringon one sidewall of the upper receiving container 140. Here, the upperreceiving container 140 may be formed in a variety of shapes accordingto a method of receiving the liquid crystal panel assembly 130, theoptical sheets 141, the alignment plate 143, the light source 142, andthe reflection sheet 146. Meanwhile, a recess on which the alignmentplate 143 having the light source 142 disposed thereon may be providedat one or both sides of the upper receiving container 140.

The optical sheets 141 are disposed on the upper surface of the lightsource 142 and are used to diffuse and condense light transmitted fromthe light source 142. The optical sheets 141 may include a diffusionsheet, a prism sheet, a protective sheet, and the like, in one example.

The diffusion sheet placed between the light source 142 and the prismsheet is used to disperse the light emitted from the light source 142and to prevent light from being partially concentrated. The prism sheetis formed in such a way that a trigonal prism is formed in apredetermined arrangement at the upper side of the prism sheet. Theprism sheet generally includes two sheets and is used to condense lightdiffused from the diffusion sheet when each prism arrangement isdisposed to cross each other at a predetermined angle, in a directionperpendicular to the liquid crystal panel 135. As such, most of thelight that passes through the prism sheet proceeds in a horizontaldirection and brightness is uniformly distributed on the protectivesheet. The protective sheet formed on the prism sheet is used to protectthe surface of the prism sheet and to diffuse light so as to make thediffusion of light uniform.

The light source 142 provides light to the LCD device 100 that cannotemit light by itself. The light source 142 may include a plurality oflamps arranged on the alignment plate 143 in a first direction to thenbe disposed at one or both sides of the optical plate 200. The alignmentplate 143 may be attached to a light source cover to reduce loss of thelight emitted from the light source 142. The light source 142 may be,but is not limited to, a point light source such as a light emittingdiode (LED), a linear light source such as a cold cathode fluorescentlamp (CCFL), a hot cathode fluorescent lamp (HCFL), or an externalelectrode fluorescent lamp (EEFL), or any other type of light source. Inthe following examples, embodiments of the invention are described withregard to the light source 142 using a point light source as an example.

The optical plate 200 is disposed below the upper receiving container140 so that at least one side thereof faces the light source 142 andguides the light emitted from the light source 142. In this embodiment,the optical plate 200 serves to focus light and adjust the quantity oflight. The optical plate 200 may be a transparent material capable ofeffectively guiding light, for example, a material having a highrefractive index such as polymethylmethacrylate-series resin (PMMA),polycarbonate-series resin (PC), etc.

Light which is incident into a lateral side of the optical plate 200made of the above-mentioned material has an incident angle that is notgreater than a critical angle of the optical plate 200, the incidentlight travels inside the optical plate 200. When the light is incidentinto a top surface or a bottom surface of the optical plate 200, theincidence of angle is greater than a critical angle, so that theincident light is not emitted outside the optical plate 200 but issubstantially uniformly dispersed in the optical plate 200. Scatteringpatterns (not shown) are formed on at least one of the top and bottomsurfaces of the optical plate 200. The scattering patterns transmit thelight that is incident into the top or bottom surface of the opticalplate 200 to the liquid crystal panel 135. The shape of the opticalplate 200 will later be described in detail.

The reflection sheet 146 is disposed below the optical plate 200 andreflects light upward from below the optical plate 200. The reflectionsheet 146 reflects the light that is not reflected by fine dot patternsformed at the rear side of the optical plate 200 into the emission sideof the optical plate 200 so that loss of light incident into the liquidcrystal panel 135 may be reduced and the uniformity of light transmittedto the emission side of the optical plate 200 may be improved. Thereflection sheet 146 extends to the lower portion of the alignment plate143 from the lower side of the optical plate 200, thereby suppressinglight leakage between the alignment plate 143 and the optical plate 200.

The upper receiving container 140 may be hook-coupled to the lowerreceiving container 160. For example, a hook 145 may be formed along anouter side of the sidewall of the upper receiving container 140, and ahook insertion hole 162 corresponding to the hook 145 may be formed at aside of the lower receiving container 160. Thus, the lower receivingcontainer 160 is aligned with the lower portion of the upper receivingcontainer 140 so that the hook 145 formed in the upper receivingcontainer 140 is inserted into the hook insertion hole 162 of the lowerreceiving container 160 so that the upper receiving container 140 andthe lower receiving container 160 may be combined with each other. Inaddition, the upper receiving container 140 and the lower receivingcontainer 160 may be coupled to each other by various means and methods.

Hereinafter, an optical plate for the liquid crystal display deviceshown in FIG. 1 will be described in detail according to one or moreembodiments with reference to FIGS. 2 through 4B. FIG. 2 is aperspective view showing an optical plate for the liquid crystal displaydevice shown in FIG. 1, and FIG. 3 is a view showing a positionalrelationship between an optical plate and a light source when viewed inthe Y-axis direction shown in FIG. 2.

Referring to FIGS. 1 through 3, the optical plate 200 according to thepresent embodiment is constructed to have different thicknessesaccording to its position.

The optical plate 200 has a substrate composed of surfaces 210, 220,230, and 270 having a uniform thickness, and a height-varying portion,e.g., a curved portion 250, formed on one surface 220 of the substrate'ssurfaces 210, 220, 230, and 270 facing the reflection sheet 146.

Each of the substrate's surfaces 210, 220, 230, and 270 may be shaped asa rectangle having a predetermined thickness TX, for example.

The curved portion 250 may be formed on the one surface 220 of thesubstrate's surfaces 210, 220, 230, and 270. The curved portion 250 mayhave a plurality of convex portions 240 a and a plurality of concaveportions 240 b which are alternately arranged. Here, each of the convexportions 240 a comprises a portion having a height greater than anaverage height t₂ between the surface 220 of the substrate's surfaces210, 220, 230, and 270 and the curved portion 250. Each of the concaveportions 240 b comprises a portion having a height smaller than theaverage height t₂ between the other surface 230 of the substrate'ssurfaces 210, 220, 230, and 270 and the curved portion 250. The minimumheight of the concave portions 240 b may correspond to positionscontacting the substrate's surfaces 210, 220, 230, and 270, and themaximum height T₂ of the convex portions 240 a may correspond to aposition having a height twice the average height t₂ of the curvedportion 250.

The convex portions 240 a and the concave portions 240 b are alternatelyarranged at a regular spacing, forming a sine curve. The amplitude A₁ ofthe sine curve or the average height t₂ of the curved portion 250 may bein the range of about 0.1% to about 10% of the thickness of thesubstrate's surfaces 210, 220, 230, and 270 in consideration of thebrightness uniformity of the LCD device 100. Under these conditions, thebrightness levels viewed at front and side surfaces of the liquidcrystal panel 135 may become uniform.

The plurality of light sources 142 are arranged along the firstdirection, e.g., the X-axis direction, at a predetermined pitch P, sothat light may be emitted to the one surface 210 of the optical plate200. The pitch P between each of the plurality of light sources 142 mayrange from about 5 to about 15 μm, and may vary according to the sizeand product features of the LCD device 100. The light sources 142 may beformed on the one surface 210 of the optical plate 200 having theconcave portions 240 b. The thicker the optical plate 200, the more thelight received therein, and vice versa, and the portions where theplurality of light sources 142 are arranged have a larger number oflight sources than the portions where the plurality of light sources 142are spaced apart from each other. Accordingly, the light sources 142 arearranged in the concave portions 240 b and the amplitude A₁ of the sinecurve formed by the curved portion 250 or the average height t₂ of thecurved portion 250 may be adjusted to be in the range of about 0.1% toabout 10% of the thickness of the substrate's surfaces 210, 220, 230,and 270, thereby providing the LCD device 100 with brightnessuniformity.

The pitch P between each of the plurality of light sources 142 maycorrespond to a spacing B between adjacent concave portions 240 b.

Meanwhile, the convex portions 240 a and the concave portions 240 b mayextend along a second direction substantially perpendicular to the first(X-axis) direction, e.g., the Y-axis direction. That is to say, theconvex portions 240 a and the concave portions 240 b may be shaped of ahemispherical column extending in the second direction, i.e., the Y-axisdirection.

In the present embodiment, the convex portions 240 a and the concaveportions 240 b may have a prism pattern 260. The prism pattern 260focuses the light emitted from the light source 142 to the liquidcrystal panel 135, and improves brightness uniformity of the LCD device100.

The prism pattern 260 may extend in parallel to the convex portions 240a and the concave portions 240 b in the second direction, i.e., theY-axis direction. The prism pattern 260 may be shaped of a triangularcolumn arranged along the convex portions 240 a and the concave portions240 b. In the present embodiment, the prism pattern 260 may have thesame height throughout the optical plate 200 from one end to the otherside, that is, from an end indicated by K-K′ to the opposite endindicated by L-L′.

The vertical angle α of the prism pattern 260 may range from about 90°to about 150° in consideration of, for example, focusing efficiency. Aradial direction of the prism pattern 260 formed on the convex portions240 a and the concave portions 240 b may be perpendicular to the othersurface 230 of the substrate's surfaces 210, 220, 230, and 270, theZ-axis direction.

In the LCD device 100 according to this embodiment, the curved portion250 and the prism pattern 260 may be formed of the same material as thesubstrate's surfaces 210, 220, 230, and 270, and may be integrallyformed with the substrate's surfaces 210, 220, 230, and 270. In thisembodiment, the curved portion 250 may be formed by, for example,engraving one surface 220 of the substrate's surfaces 210, 220, 230, and270.

Hereinafter, brightness uniformity of the LCD device according to thefirst exemplary embodiment of the present invention and that of an LCDdevice according to a Comparative Example will be described withreference to FIGS. 1, 4A and 4B. FIGS. 4A and 4B are photographicrepresentations illustrating the distribution of brightness uniformityof the LCD device according to the first exemplary embodiment of thepresent invention and that of an LCD device according to a ComparativeExample.

Referring to FIGS. 1 and 4A, in the LCD device 100 having the curvedportion 250 of the present embodiment, the liquid crystal panel 135 hasimproved brightness uniformity, compared to the liquid crystal panel135′.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to a second exemplary embodiment of the present invention willbe described in detail with reference to FIG. 5. For the convenience ofexplanation, components each having the same function for describing theembodiment shown in FIG. 1 are respectively identified by the samereference numerals, and their repetitive description will be omitted orbriefly made. FIG. 5 is a perspective view showing an optical plate fora liquid crystal display device according to a second exemplaryembodiment of the present invention.

Referring to FIG. 5, in the optical plate 201 of the present embodiment,the curved portion 250 and the prism pattern 260 are formed on a lightquantity adjusting portion 301 separately from the substrate's surfaces210, 220, 230, and 270, and disposed on the substrate's surfaces 210,220, 230, and 270. In detail, the curved portion 250 is formedseparately from the substrate's surfaces 210, 220, 230 that are ofsubstantially flat-type and then disposed thereon. The curved portion250 may be attached to the substrate's surfaces 210, 220, 230, and 270using, for example, a transparent adhesive agent or a double-sided tape.The curved portion 250 and the prism pattern 260 may be formed of thesame material as the substrate's surfaces 210, 220, 230, and 270.However, according to one or more embodiments, the curved portion 250and the prism pattern 260 may be formed of different materials than thesubstrate's surfaces 210, 220, 230, and 270.

The curved portion 250 and the prism pattern 260 may be formed of amonomer or copolymer such as polymethylmethacrylate (PMMA) orpolyethyleneterephthalate, a transparent resin such as polycarbonate orpolystyrene, a light-transmitting material such as transparent glass ortransparent ceramic. If the curved portion 250 and the prism pattern 260are formed separately from the substrate's surfaces 210, 220, 230, and270, the fabrication efficiency may be improved according to separateand specialized fabrication processes. Furthermore, if the curvedportion 250 and the prism pattern 260 are formed of different materialsfrom the substrate's surfaces 210, 220, 230, and 270, the optical plate201 having various light efficiencies may be fabricated.

According to this embodiment, the curved portion 250 and the prismpattern 260 may be integrally formed with each other. Alternatively, theprism pattern 260 may be separately formed from the curved portion 250and then attached to the curved portion 250.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to a third exemplary embodiment of the present invention willbe described in detail with reference to FIG. 6. FIG. 6 is a perspectiveview showing an optical plate for a liquid crystal display deviceaccording to a third exemplary embodiment of the present invention.

Referring to FIG. 6, a difference in the height of the curved portion250 according to the present embodiment gradually decreases along thesecond direction, i.e., Y-axis direction, from one end of the opticalplate 202 to the other end thereof, that is, from an end indicated byK-K′ to the opposite end indicated by L-L′.

In other words, a height difference between each of convex portions 242a and each of concave portions 242 b is T₂ at one end of the opticalplate 202, as indicated by K-K′, and gradually decreases in the seconddirection, i.e., the Y-axis direction. Finally, the convex portions 240a and the concave portions 240 b may not be formed at the other end ofthe optical plate 202, as indicated by L-L′.

A plurality of light sources 142 are arranged on the optical plate 202in the first direction, e.g., the X-axis direction, and the convexportions 242 a and the concave portions 242 b extend along the seconddirection, e.g., the Y-axis direction. Accordingly, a difference in thebrightness is generated between an area where the light sources 142 areprovided and an area where the light sources 142 are not provided. Thebrightness difference may gradually decrease in the second direction ofthe optical plate 202, e.g., the Y-axis direction. The brightnessdifference may become zero at the end of the optical plate 202, asindicated by L-L′. Thus, the convex portions 242 a and the concaveportions 242 b used for adjusting the quantity of light may not beprovided at the end of the optical plate 202, as indicated by L-L′.

Meanwhile, a prism pattern 262 may be formed to have the same heightthroughout the optical plate 202 from an end indicated by K-K′ to theopposite end indicated by L-L′. At the end L-L′ of the optical plate202, the prism pattern 262 may be formed on one surface 220 of thesubstrate's surfaces 210, 220, 230, and 272 that are of substantiallyflat-type.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to a fourth exemplary embodiment of the present invention willbe described in detail with reference to FIG. 7. FIG. 7 is a perspectiveview showing an optical plate for a liquid crystal display deviceaccording to a fourth exemplary embodiment of the present invention.

Referring to FIG. 7, the optical plate 203 of the present embodiment issubstantially the same as that of the third embodiment, except that thecurved portion 250 and a prism pattern 263 are formed separately fromsubstrate's surfaces 210, 220, 230, and 273 and then disposed on a lightquantity adjusting portion 303. The curved portion 250 and the prismpattern 263 are substantially the same as those of the second embodimentin view of the materials and fabrication method used.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to a fifth exemplary embodiment of the present invention willbe described in detail with reference to FIGS. 8 through 11B. FIG. 8 isa perspective view showing an optical plate for a liquid crystal displaydevice according to a fifth exemplary embodiment of the presentinvention, FIG. 9 is a perspective view showing the bottom surface ofthe optical plate shown in FIG. 8, and FIG. 10 is a view showing apositional relationship between an optical plate and a light source whenviewed in a direction of the Y axis shown in FIG. 9.

Referring to FIGS. 8 and 9, the optical plate 204 of the presentembodiment includes a prism pattern 264. The prism pattern 264 mayextend on one surface 234 of a plurality of substrate's surfaces 210,224, and 234 along the first direction, i.e., the X-axis direction anddisposed in parallel to the first direction. In other words, unlike inthe previous embodiments, the prism pattern 264 of the presentembodiment is formed on one surface 234 of the substrate's surfaces 210,224, and 234, rather than the opposite surface 224 having a liquidcrystal panel (not shown) formed thereon. That is, the prism pattern 264is formed on the surface 234 of the substrate's surfaces 210, 224, and234 facing the reflection sheet (146 of FIG. 1). In addition, the prismpattern 264 of the present embodiment extends along the same directionas light sources 142 arranged in the first direction, i.e., the X-axisdirection. In order to emit the incident light in a directionperpendicular to the direction of incidence, i.e., in the Z-axisdirection, the prism pattern 264 may be formed at a predetermined anglewith respect to the one surface 234 of the substrate's surfaces 210,224, and 234. That is, an angle β formed by the surface facing the lightsources 142 and the surface 234 of the substrate's surfaces 210, 224,and 234 may range from about 35° to about 45°, and an angle γ formed bythe plane opposite to the surface facing the light sources 142 and thesurface 234 of the substrate's surfaces 210, 224, and 234 may range fromabout 2° to about 10°.

The prism pattern 264 may include a height-varying portion. That is, atop surface of the prism pattern 264 comprises a plurality of convexpatterns 264 a each having a greater height than the average height h₄(illustrated, for example, in FIG. 10) of the prism pattern 264 and aplurality of concave patterns 264 b each having a smaller height thanthe average height h₄ of the prism pattern 264, wherein the concavepatterns 264 b and the convex patterns 264 a may alternate. In otherwords, the convex pattern 264 a and the concave pattern 264 b mayalternate each other at a regular spacing, forming a sine curve. Theheight H₄ of the prism pattern 264 may be uniform at the one end N-N′ ofthe optical plate 204 and the other end O-O′ of the optical plate 204,as indicated by M-N′ and M-N, respectively.

Referring to FIGS. 8 through 10, the light sources 142 may be arrangedon the surface 210 of the substrate's surfaces 210, 224, and 234.Specifically, a predetermined pitch P in which the light sources 142 arearranged may be the same as a spacing E in which the concave patterns264 b are spaced apart from each other. Accordingly, an amount of lightthat is incident light from the light sources 142 and exits through theoptical plate 204 may become similar to that of light at the area wherethe light sources 142 are not provided. In order to allow thedistribution of brightness uniformly viewed from a liquid crystal panel,a height difference A₄ between a maximum height H₄ of the prism pattern264 at the convex pattern 264 a and the average height h₄ of the prismpattern 264 may be adjusted to be in a range of about 0.1% to about 10%.Accordingly, brightness uniformity of the liquid crystal panel may beachieved, both in the area where the light sources 142 are arranged andthe spacing between adjacent light sources 142.

According to this embodiment, the substrate's surfaces 210, 224, and 234and the prism pattern 264 may be integrally formed with each other usingthe same material.

Hereinafter, brightness uniformity of the LCD device according to thefifth exemplary embodiment of the present invention and that of an LCDdevice according to a Comparative Example will be described withreference to FIGS. 11A and 11B. FIGS. 11A and 11B are photographicrepresentations illustrating the distribution of brightness uniformityof the LCD device according to the fifth exemplary embodiment of thepresent invention and that of the LCD device according to a ComparativeExample.

Referring to FIG. 11A, in the LCD device 100 according to the presentembodiment, in which the convex portions 264 a and the concave portions264 b are provided in the prism pattern 264, brightness uniformity ofthe liquid crystal panel 135 is improved, compared to that of the liquidcrystal panel 135′ according to the Comparative Example.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to a sixth exemplary embodiment of the present invention willbe described in detail with reference to FIGS. 12 and 13. FIG. 12 is aperspective view showing an optical plate for a liquid crystal displaydevice according to a sixth exemplary embodiment of the presentinvention, and FIG. 13 is a perspective view showing the bottom surfaceof the optical plate shown in FIG. 12.

Referring to FIGS. 12 and 13, in the optical plate 205 of the presentembodiment, a prism pattern 365 of the optical plate 205 may beseparately formed from substrate's surfaces 210, 224, and 234 and thendisposed on one surface 234 of the substrate's surfaces 210, 224, and234. In addition, the prism pattern 364 may be formed of a materialdifferent from that of the substrate's surfaces 210, 224, and 234. Theoptical plate 205 of the present embodiment is substantially the same asthat of the fifth embodiment except that the prism pattern 365 and thesubstrate's surfaces 210, 224, and 234 are formed separately from eachother using different materials. The prism pattern 365 may be shaped ofa film made of a monomer or copolymer such as polymethylmethacrylate(PMMA) or polyethyleneterephthalate, a transparent resin such aspolycarbonate or polystyrene, a light-transmitting material such astransparent glass or transparent ceramic.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to a seventh exemplary embodiment of the present inventionwill be described in detail with reference to FIGS. 14 and 15. FIG. 14is a perspective view showing an optical plate for a liquid crystaldisplay device according to a seventh exemplary embodiment of thepresent invention, and FIG. 15 is a perspective view showing the bottomsurface of the optical plate shown in FIG. 14.

Referring to FIGS. 14 and 15, in the optical plate 206 of the presentembodiment, light sources 142 are arranged on one surface 210 ofsubstrate's surfaces 210, 224 and 234 in a first direction, i.e., theX-axis direction. A height H₄ of a prism pattern 266, as indicated byM-N or M′-N′, gradually decreases along a second direction, i.e., theY-axis direction perpendicular to the first direction, i.e., the X-axisdirection. The height of the prism pattern 266 may become zero at oneend O-O′ of the substrate's surfaces 210, 224, and 234. In other words,the prism pattern 266 may not be provided at the end O-O′ of thesubstrate's surfaces 210, 224, and 234. In this case, a heightdifference of the prism pattern 266 between a convex pattern 266 a and aconcave pattern 266 b is maximum at the end N-N′ of the substrate'ssurfaces 210, 224, and 234, and the height difference of the prismpattern 266 between a convex pattern 266 a and a concave pattern 266 bmay become zero at the end O-O′ of the substrate's surfaces 210, 224,and 234.

Since the light sources 142 are arranged at the end N-N′ of thesubstrate's surfaces 210, 224, and 234, a brightness differenceoccurring between the area where the light sources 142 are disposed andthe spacing between adjacent light sources 142 is reduced by the heightdifference between a convex pattern 266 a and a concave pattern 266 b.However, since the end O-O′ of the substrate's surfaces 210, 224, and234 is considerably spaced apart from the light sources 142, thebrightness difference of the light sources 142 may be mitigated, so thata process of forming the prism pattern 266 may be omitted.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to an eighth exemplary embodiment of the present inventionwill be described in detail with reference to FIGS. 16 and 17. FIG. 16is a perspective view showing an optical plate for a liquid crystaldisplay device according to an eighth exemplary embodiment of thepresent invention, and FIG. 17 is a perspective view showing the bottomsurface of the optical plate shown in FIG. 16.

Referring to FIGS. 16 and 17, in the optical plate 207 of the presentembodiment, a prism pattern 367 of the optical plate 207 may beseparately formed from substrate's surfaces 210, 224, and 234 and thendisposed on one surface 234 of the substrate's surfaces 210, 224, and234. In addition, the prism pattern 367 may be formed of a materialdifferent from that of the substrate's surfaces 210, 224, and 234. Theoptical plate 207 of the present embodiment is substantially the same asthat of the seventh embodiment except that the prism pattern 367 and thesubstrate's surfaces 210, 224, and 234 are formed separately from eachother using different materials. That is, a height difference between aconvex pattern 367 a and a concave pattern 367 b gradually decreasesalong a second direction, i.e., the Y-axis direction, from one surface210 of the substrate's surfaces 210, 224, and 234 to the other surface.The height difference between the convex pattern 367 a and the concavepattern 367 b may become zero at the other surface of the substrate'ssurfaces 210, 224, and 234.

Hereinafter, an optical plate for a liquid crystal display deviceaccording to a ninth exemplary embodiment of the present invention willbe described in detail with reference to FIGS. 18 and 19. FIG. 18 is aperspective view showing an optical plate for a liquid crystal displaydevice according to a ninth exemplary embodiment of the presentinvention, and FIG. 19 is a perspective view showing the bottom surfaceof the optical plate shown in FIG. 18.

Referring to FIGS. 18 and 19, the optical plate 208 includes aheight-varying portion, e.g., a curved portion 250, and a plurality offirst prism patterns 264. The height-varying portion, e.g., the curvedportion 250 comprises a plurality of convex patterns 240 a and aplurality of concave patterns 240 b, and is formed on one surface 220 ofsubstrate's surfaces 210, 220, 234, and 270, not facing a reflectionsheet 146. The plurality of first prism patterns 264 extend on onesurface 234 of substrate's surfaces 210, 224, and 234 along the firstdirection, i.e., the X-axis direction.

Each of the first prism patterns 264 may include a height-varyingportion. A top surface of each of the first prism patterns 264 comprisesthe plurality of convex patterns 264 a each having a greater height thanthe average height h₄ (as illustrated, for example, in FIG. 10) of thefirst prism patterns 264, and the plurality of concave patterns 264 beach having a smaller height than the average height h₄ of the firstprism patterns 264, wherein the concave patterns 264 b and the convexpatterns 264 a may alternate.

A liquid crystal panel (not shown) may be disposed at a side of thecurved portion 250.

The convex portions 240 a are formed to have a height greater than theaverage height from one surface 220 of substrate's surfaces 210, 220,234, and 270 to the curved portion 250, and the concave portions 240 bare formed to have a height smaller than the surface 220 of thesubstrate's surfaces 210, 220, 234, and 270 to the curved portion 250.The concave portions 240 b alternate with the convex portions 240 a. Theconvex portions 240 a and the concave portions 240 b may extend in thesecond direction, i.e., the Y-axis direction, substantiallyperpendicular to the first direction, i.e., the X-axis direction.

Second prism patterns 260 may be formed on the top surface of the curvedportion 250. The second prism patterns 260 may be formed on the convexportions 240 a or the concave portions 240 b in parallel thereto in thesecond direction, i.e., the Y-axis direction.

A plurality of light sources 142 are arranged on one surface 210 of thesubstrate's surfaces 210, 220, 234, and 270 in the first direction,i.e., the X-axis direction, and are capable of emitting light. Each ofthe plurality of light sources 142 is disposed in vicinity of theconcave portions 240 b and the concave patterns 264 b, thereby improvingbrightness uniformity of light emitted to the liquid crystal panel. Apitch between each of the plurality of light sources 142 may be the sameas a spacing between adjacent concave portions 240 b and adjacentconcave patterns 264 b.

In other words, the optical plate 208 of the present embodiment is acombination of the optical plates of the first and fifth embodiments ofthe present invention. However, a height difference between the averageheight (not shown) of the curved portion 250 to the thickness of thesubstrate's surfaces 210, 220, 234, and 270 and the maximum height (notshown) of the prism pattern 264 to the average height (not shown) of theprism pattern may be adjusted to obtain a different height differencethan the previous embodiments.

Alternatively, although not shown, the optical plate 208 of the presentembodiment may be a combination of one of the optical plates of thefirst through fourth embodiments of the present invention and one of theoptical plates of the fifth through eighth embodiments of the presentinvention.

That is, the height of the first prism pattern 264 may graduallydecrease along the second direction e.g., the Y-axis direction,substantially perpendicular to the first (X-axis) direction. A heightdifference between the convex portion 240 a and the concave portion 240b gradually decreases along the second direction, e.g., the Y-axisdirection. At least one of the curved portion 250, the second prismpattern 260, and the first prism pattern 264 may be integrally formedwith the substrate's surfaces 210, 220, 234, and 270 using the samematerial. Alternatively, at least one of the curved portion 250, thesecond prism pattern 260, and the first prism pattern 264 may be formedseparately from the substrate's surfaces 210, 220, 234, and 270.

While embodiments of the present invention have been particularly shownand described it will be understood by those of ordinary skill in theart that various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present disclosure as definedby the following claims. It is therefore desired that the presentembodiments be considered in all respects as illustrative and notrestrictive, reference being made to the appended claims rather than theforegoing description to indicate the scope of the disclosure.

1. A liquid crystal display device comprising: a reflection sheetreflecting light; an optical plate including a substrate for guidinglight, a height-varying portion formed on one surface of the substrate,not facing the reflection sheet, and a prism pattern formed on theheight-varying portion; and a plurality of light sources arranged on onelateral surface of the optical plate in a first direction so as tocorrespond to a position of the height-varying portion having a heightnot greater than an average height from the one surface of the substrateto the height-varying portion, wherein the prism pattern extends in asecond direction substantially perpendicular to the first direction, andthe average height is in a range of about 0.1% to about 10% thethickness of the substrate.
 2. The liquid crystal display device ofclaim 1, wherein the height-varying portion is a curved portion formedon one surface of the substrate at a regular interval, and the curvedportion is composed of a plurality of convex portions each having aheight greater than the average height, and a plurality of concaveportions each having a height smaller than the average height andalternating with the convex portions.
 3. The liquid crystal displaydevice of claim 2, wherein the prism pattern extends in parallel to theplurality of convex portions or the plurality of concave portions in thesecond direction.
 4. The liquid crystal display device of claim 2,further comprising a liquid crystal panel disposed on the curvedportion, wherein the curved portion and the prism pattern are integrallyformed with the substrate using the same material as the substrate. 5.The liquid crystal display device of claim 2, further comprising aliquid crystal panel disposed on the curved portion, wherein the curvedportion and the prism pattern are formed of a different material fromthe substrate and disposed on the substrate.
 6. The liquid crystaldisplay device of claim 5, wherein the curved portion and the prismpattern are formed of a film disposed on the substrate.
 7. The liquidcrystal display device of claim 1, wherein a height difference in theheight-varying portion gradually decreases along the second direction.8. The liquid crystal display device of claim 2, wherein the pluralityof light sources are point light sources, and a pitch between each ofthe plurality of light sources is substantially the same as a spacingbetween the concave portions.
 9. A liquid crystal display devicecomprising: a reflection sheet reflecting light; an optical plateincluding a substrate for guiding light, and a plurality of prismpatterns extending in parallel to one another in a first direction onone surface of the substrate facing the reflection sheet; and aplurality of light sources arranged on one lateral surface of theoptical plate in the first direction, wherein each of the prism patternshas a height-varying portion and the plurality of light sources isarranged so as to correspond to a position of the height-varying portionhaving a height not greater than an average height of the plurality ofprism patterns.
 10. The liquid crystal display device of claim 9,wherein the height-varying portion is composed of a plurality of convexportions each having a height greater than the average height of theplurality of prism patterns, and a plurality of concave portions eachhaving a height smaller than the average height of the plurality ofprism patterns and alternating with the convex portions.
 11. The liquidcrystal display device of claim 10, wherein a height difference betweena maximum height of the prism pattern at the convex pattern and theaverage height of the prism patterns is adjusted to be in a range ofabout 0.1% to about 10% of the average height of the prism patterns. 12.The liquid crystal display device of claim 9, further comprising aliquid crystal panel disposed on the other surface of the substratefacing the surface of the substrate, wherein the prism patterns areintegrally formed with the substrate using the same material as thesubstrate.
 13. The liquid crystal display device of claim 9, furthercomprising a liquid crystal panel disposed on the other surface of thesubstrate facing the surface of the substrate, wherein the prismpatterns are formed of a different material from the substrate anddisposed on the substrate.
 14. The liquid crystal display device ofclaim 13, wherein the prism patterns are formed of a film disposed onthe substrate.
 15. The liquid crystal display device of claim 9, whereinthe height of the prism patterns gradually decreases along a seconddirection substantially perpendicular to the first direction.
 16. Theliquid crystal display device of claim 10, wherein the plurality oflight sources are point light sources, and a pitch between each of theplurality of light sources is substantially the same as a spacingbetween the concave portions.
 17. A liquid crystal display devicecomprising: a reflection sheet reflecting light; an optical plateincluding a substrate for guiding light, a first height-varying portionformed on one surface of the substrate, not facing the reflection sheet,and a plurality of first prism patterns extending on the other surfaceof the substrate facing the reflection sheet in parallel to one anotherin a first direction; a plurality of light sources arranged on onelateral surface of the optical plate in the first direction; and aplurality of second prism patterns extending on the first height-varyingportion in a second direction substantially perpendicular to the firstdirection; wherein each of the plurality of first prism patterns has asecond height-varying portion, and the plurality of light sources arearranged so as to correspond to a position of the first height-varyingportion having a height not greater than a first average height from theone surface of the substrate to the height-varying portion and aposition of the second height-varying portion having a height notgreater than a second average height of the first prism patterns. 18.The liquid crystal display device of claim 17, wherein the firstheight-varying portion is a curved portion formed on one surface of thesubstrate at a regular interval, and is composed of a plurality ofconvex portions each having a height greater than the first averageheight, and a plurality of concave portions each having a height smallerthan the first average height and alternating with the convex portions.19. The liquid crystal display device of claim 17, wherein the secondheight-varying portion is composed of a plurality of convex patternseach having a height greater than the second average height, and aplurality of concave patterns each having a height smaller than thesecond average height and alternating with the convex patterns.
 20. Theliquid crystal display device of claim 17, wherein the height of thefirst prism patterns gradually decreases along the second directionsubstantially perpendicular to the first direction.
 21. The liquidcrystal display device of claim 18, wherein the second prism patternsextend along the second direction in parallel to the convex portions orthe concave portions.
 22. The liquid crystal display device of claim 18,wherein a height difference between each of the convex portions and eachof the concave portions gradually decreases along the second direction.23. The liquid crystal display device of claim 17, further comprising aliquid crystal panel disposed on the first height-varying portion,wherein at least one of the first height-varying portion, first prismpatterns and the second prism patterns is integrally formed with thesubstrate using the same material as the substrate.
 24. The liquidcrystal display device of claim 17, further comprising a liquid crystalpanel disposed on the first height-varying portion, wherein at least oneof the first height-varying portion, first prism patterns and the secondprism patterns is formed of a different material than the substrate anddisposed on the substrate.
 25. The liquid crystal display device ofclaim 18, wherein the second height-varying portion is composed of aplurality of convex patterns each having a height greater than thesecond average height, and a plurality of concave patterns each having aheight smaller than the second average height and alternating with theconvex patterns, and wherein the plurality of light sources furthercomprises point light sources, and a pitch between each of the pluralityof light sources is substantially the same as a spacing between each ofthe concave patterns and each of the concave portions.